This invention, as stated in the heading to this descriptive report, concerns a purification system for wastewater coming from fruit and vegetable processing plants and phytosanitary treatment in the field, with which notable relevant and advantageous characteristics are contributed compared to present conventional purification systems.
The wastewater from chemical products generated in fruit and vegetable processing plants is purified in the different systems of application that are used: drenchers (pallet dousers), fungicide applicators, wax applicators, treatment lines and treatment pools, etc., along with the purification of waste liquid left over from phytosanitary treatments carried out in the field.
For purification of water contaminated with pesticides, a treatment sequence is currently followed of: conventional filtrationxe2x80x94activated carbonxe2x80x94biological degradation, as considered in the decontamination system of invention patent with publication number ES2050909 referring to the detoxification of solutions that could contain toxic substances such as pesticide residues.
The system consists of a tank where the liquid is collected, fitted with a basket made of a grating with a hole size of 0.8 mm. The tank has an air inlet for the introduction of compressed air that is mixed with the liquid, thereby improving the degradation of toxic materials in the liquid.
The toxicity level of the water in the tank is established so that, depending on this level, the water is transferred to the appropriate decontamination subsystems.
With a high level of toxicity, the water is conducted to a retaining tank, fed with a constant source of compressed air.
The treated liquid passes through an earth bed reactor. The reactor includes a layer of earth on a series of permeable concrete blocks. The liquid is applied to the upper part of the layer of earth by means of a network of conventional drip irrigation pipes. The earth bed reactor contains microorganisms that utilise the organic materials employed as the pesticide as a source of nutrients.
The liquid is diverted from the earth filter to an activated carbon filter. This filter can include a layer of alumina with potassium permanganate for oxidising toxic materials.
The final phase of the decontamination system is a settling basin, i.e., an open permeable pool. This basin does not just eliminate a substantial part of the water by evaporation, it also improves the quality of the water by eliminating traces of pesticides. The basin is stocked with species of animals and plants for the additional degradation of the organic material contained in the water.
If wished, a conventional ozonisation system can be included in the system for the introduction of ozone in the rotation tank.
Another system that is known has the treatment sequence: filtration beds with carbonxe2x80x94degradation with specific microorganisms. This method and system for treatment of water is considered in invention patent with publication number WO 94/29224. It considers a system for the purification of water with a high content of organic components, such as waste from agricultural chemicals, and a low DBO.
A porous material is used as a filtration medium, carbon, on which is placed a substrate of specific microorganism (from the Pseudomonas group). The water enters into contact with these microorganisms under aerobic conditions.
The system consists of five tanks in series, through which the wastewater is made the flow.
Following a treatment sequence of: activated carbonxe2x80x94filtration, we can mention the utility model number 9301506 referring to a wastewater purifier consisting of a vat or trough provided with a stirrer and a tank that links to it underneath via an intermediate bypass valve. Contaminated liquid reaches the vat from the fruit and vegetable treatment zone by means of a pipe, driven by a pump in such a way that the contaminated liquid contained in the trough along with a quantity of activated carbon is removed by a stirrer.
When the stirrer is stopped, the bypass valve is opened and the contaminated elements adhered to the carbon fall by means of settlement down to the lower tank, from where they are extracted.
There also exist other filters and a filtration column for totally cleaning the content of the vat of any impurities. The liquid is made to pass through filters in such a way that, by means of closing certain stopcocks before and after an impulsion pump and opening others, the circulation of the fluid from the fruit and vegetable treatment zone towards the vat is prevented, while on the other hand, the circulation of the fluid coming from the vat via the filter circuit is facilitated.
Patent of invention with publication number 0447923A1, referring to a polymer adsorption system, reports an effective filtration medium for oils and greases, liquid hydrocarbon, sterols, organic pesticides and other inert liquid compounds with organic bonds and their mixtures.
The filtration medium consists of polyvinyl acetate, whose particles have a porous structure. The polyvinyl acetate comes in sheet form, in particular constructed in the form of a sandwich containing particles of polyvinyl butyral, and there is also polyvinyl acetate in form of multi-chamber structures.
Using a treatment sequence of: biological treatment with specific strains, mention can be made of invention patent ES2095193 referring to the use of bacterial strains of the Pseudomonas genera PCH3 and GCH1 for the bio-restoration of soils and purification of water contaminated with acetamide-based herbicides. This system is characterised by using at least one of the Pseudomonas strains PCH3 and GCH1 for the bio-transformation of water contaminated with herbicides. For this, the necessary nutrients have to be added in order to achieve optimisation of the bio-transformation. The water has to be inoculated for treating in a culture with at least one of the microorganisms mentioned above, which must be immobilised on a solid support of a ceramic, synthetic or organic nature. The immobilised microorganism is added as a bio-catalyst to a bio-reactor, with the conditions being regulated in order to optimise the transformation process of the contaminant compounds.
With a treatment sequence: filtration ultraviolet, invention patent ES2027366 can be mentioned, which discusses an apparatus for water treatment. The apparatus is designed for the purification of drinking water and contains a system for purifying toxic compounds; it is capable of retaining trace quantities.
This apparatus consists of a head with an opening for the entrance of water and another for the outlet, and a set of fitted parts that include filtration means and radiation means.
The filtration means can consist of mechanical fibres and/or chemical adsorption material, and is preferably of the activated carbon type with granular transverse section.
The internal diameter of the filtration means is somewhat greater than the external diameter of the irradiation means. The irradiation means includes an ultraviolet lamp, with or without ozone.
Also using a treatment sequence: (ozone)xe2x80x94ultravioletxe2x80x94activated carbon, mention can be made of the invention patent WO94/25401, concerning a water purification unit. This system is designed for the purification of drinking water and contains a retaining system for toxic compounds prepared for retaining traces quantities. The water to be purified flows under a powerful source of ultraviolet radiation and then passes through an activated carbon filter fitted on the ultraviolet source. The effluent from the filter is again passed through the ultraviolet radiation source. This source eliminates the microorganisms present and the filter retains particles and other compounds.
An ozone generator can be incorporated into the water inlet in order to boost the destruction of microorganisms present and oxidise the undesirable components of the water.
In general terms, the purification system for wastewater coming from fruit and vegetable processing plants and phytosanitary treatment in the field, constituting the object of the invention, basically includes the following elements:
First of all, it has a settling tank, of truncated conical shape and manufactured in polyester reinforced with fiberglass, with an approximate capacity of 500 1. This tank will contain two or more outlets at different heights for the settling, one of which will be arranged so as to start at the conical base and the other at a higher level, more specifically at 50% of the height of the cylindrical part of that tank. It has a flocculent dosing system and a stirrer for producing a good mix. A filtration system for the sludge is provided at the outlet from the tank, and the sludge then passes to a filtering bag of approximately 820 mm in length and 180 mm in diameter, manufactured in single-filament nylon with a mesh-size of 60 to 75 microns. The product filtered in the bag is then passed to a collection tank of approximately 50 1 and from here it is pumped to an intermediate tank of dimensions similar to the one for settling.
From the intermediate tank, the filtered product passes to a self-cleaning ring filter, of mesh-size 75 microns, and then through some activated carbon columns, normally one to three in number, of the order of 300 1 in volume and containing approximately 100 kg of carbon. They are manufactured in polystyrene with an exterior reinforcement of fibreglass and epoxy resin.
There is a system of warning lights for indicating when the activated carbon has become exhausted, and also the necessary pumps and valves for the facility.
The wastewater is pumped from the tanks containing the drenchers using conventional pumps.
Sometimes, at the outlet from the array of activated carbon columns, an ultraviolet lamp is incorporated in order to guarantee a greater degree of purification.
The system includes a reverse-wash mechanism permitting a greater yield to be obtained from the activated carbon columns.
In order to facilitate an understanding of the invention, and forming an integral part of this descriptive report, a sheet of plans is attached containing a single figure in which, by way of illustration and not to be regarded as restrictive, the following is represented: